1. Field of the Invention
The present invention relates to a fuel transporting hose which is suitably used in a fuel pipe system of an automobile, for transporting a liquid such as gasoline or a gas.
2. Discussion of the Related Art
There are known various kinds of hoses made of various materials, for use in a fuel pipe system of an automobile or other vehicle. Such hose may be used as a fuel pipe itself or as a connector for connecting fuel pipes. For example, there is known a hose which consists of: an innermost layer made of fluororubber (FKM); an intermediate layer formed on the innermost layer and made of a rubber material, such as a copolymer of epichlorohydrin-ethylene oxide-allylglycidyl ether (ECO), acrylonitrile-butadiene rubber (NBR), and chlorosulphonated polyethylene (CSM); an outermost layer formed on the intermediate layer and made of ECO; and a reinforcing layer formed between the intermediate layer and the outermost layer, by braided reinforcing fibers.
The above-described four-layered hose including the fiber reinforcing layer has excellent properties required for its use in the fuel pipe system of the automobile, which properties include the resistance to sour gasoline which contains peroxides produced upon oxidation of gasoline at a high temperature, and the ability to prevent permeation of gasoline therethrough, in other words, gasoline impermeability. In producing the hose, however, each layer of the hose needs to be formed with a sufficiently large thickness, which requires a large amount of expensive fluororubber to be used for the innermost layer, resulting in an increased cost of manufacture of the hose. Further, the process of producing the hose includes a series of cumbersome steps, e.g., extrusion-braiding-extrusion-vulcanization.
As a fuel transporting hose for use in a fuel pipe system of an automobile or others, there is also known a hose which consists of a single layer made of a polyamide resin, and a hose which consists of a resin tube made of fluorine-contained resin, and a reinforcing layer formed by braiding a metallic wire on the outer surface of the resin tube.
While the hose consisting solely of the polyamide resin layer is available at a relatively low cost, the hose is unsatisfactory in the resistance to sour gasoline, the gasoline impermeability (including the impermeability to alcohol blended gasoline), and the flexibility. This hose is also unsatisfactory in the resistance to wear (hereinafter referred to as "wear resistance") due to its contact with other hoses when the hose is installed in a narrow space within an automobile body, and in the resistance to shocks such as that caused by stones hit by the automobile during its running (hereinafter referred to as "shock resistance"). Further, the inner wall of the hose of this type tends to be electrically charged, due to static electricity caused by friction between the inner wall and a fuel liquid such as gasoline. If a voltage higher than a give level appears across the hose, spark may take place between the hose and metallic parts of the body supporting the hose, for example, and the spark may form holes through the hose, or may cause the fuel to ignite. Thus, the hose consisting solely of the polyamide resin layer also has a problem in respect of the resistance to firing.
The other type of the above-indicated hose with the reinforcing layer in the form of the wire formed by braiding on the fluorine-contained resin tube ensures sufficiently high degrees of resistance to sour gasoline and gasoline impermeability, due to the use of the fluorine-contained resin, and also ensures high degrees of wear resistance and shock resistance, due to the use of the braided reinforcing layer. However, like the polyamide single-layer hose as described above, the hose having the fluorine-contained resin layer is unsatisfactory in the flexibility and the resistance to firing. Further, the cost of manufacturing of this type of hose is relatively high due to the use of expensive fluorine-contained resin.